- remove stable and grey buttons (#190)

...coronawarnapp/util/formatter/FormatterSubmissionHelper.kt

Corona-Warn-App/src/main/res/color/button_primary.xml

Corona-Warn-App/src/main/res/color/button_stable.xml

Corona-Warn-App/src/main/res/color/button_text_color.xml

...n-App/src/main/res/color/button_text_color_emphasized.xml

Corona-Warn-App/src/main/res/drawable/button.xml

...na-Warn-App/src/main/res/layout/fragment_risk_details.xml

...-Warn-App/src/main/res/layout/fragment_submission_tan.xml

Corona-Warn-App/src/main/res/layout/include_risk_card.xml

Corona-Warn-App/src/main/res/values-night/colors.xml

Corona-Warn-App/src/main/res/values/colors.xml

Corona-Warn-App/src/main/res/values/styles.xml